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Abstract:

To provide a substrate processing method and a semiconductor chip
manufacturing method that enable low-cost formation of a mask for etching
using plasma etching. During formation of a mask used in plasma dicing
for separating a semiconductor wafer 1 into discrete semiconductor chips
1e by means of etching using plasma processing, there is adopted a method
including printing a lyophobic liquid in an area on a rear surface 1b
that is to be an objective of etching, thereby forming a lyophobic
pattern made up of lyophobic films 3; supplying a low viscosity resin 4a
and a high viscosity resin 4b, in this sequence, to the rear surface 1b
on which the lyophobic pattern is formed, thereby forming a resin film 4
that is thicker than the lyophobic films 3 in an area where the lyophobic
films 3 are not present; and curing the resin film 4, to thus form a mask
4* that covers an area except for the area to be etched. Thus, a mask for
etching purpose can be formed at low cost without use of a high-cost
method, like photolithography.

Claims:

1. A substrate processing method for partially eliminating a substrate by
etching using plasma processing, the method comprising: a lyophobic
pattern formation step of printing, on a processing target surface of the
substrate, a lyophobic liquid to an area to be etched away and a contour
set along an outer edge of the substrate to a predetermined width,
thereby forming a lyophobic pattern; a resin film formation step of
supplying a liquid resin on the processing target surface of the
substrate on which the lyophobic pattern is formed, thereby forming a
resin film that is thicker than the lyophobic pattern in an area where
the lyophobic pattern is not formed; a mask formation step of curing the
resin film, to thus form on the processing target surface a mask for
covering an area except for the area to be etched away; a lyophobic
pattern removal step of removing the lyophobic pattern from the
processing target surface after performance of processing pertaining to
the mask formation step; an etching step of etching the substrate from
the processing target surface thereof by plasma processing after
processing pertaining to the lyophobic pattern removal step; and a mask
removal step of removing the mask from the processing target surface
after completion of processing pertaining to the etching step.

2. A semiconductor chip manufacturing method for separating a
semiconductor wafer, which has a plurality of semiconductor devices on a
circuit fabrication surface and which is affixed with a protective sheet
for protecting the circuit fabrication surface, into semiconductor chips
made up of respective semiconductor devices by means of etching using
plasma processing, the method comprising: a lyophobic pattern formation
step of printing a lyophobic liquid on scribe lines serving as borders
between semiconductor chips on a processing target surface of the
semiconductor wafer that is another side of the circuit fabrication
surface and a contour set along an outer edge of the semiconductor wafer
to a predetermined width, thereby forming a lyophobic pattern; a resin
film formation step of supplying a liquid resin on the processing target
surface of the semiconductor wafer on which the lyophobic pattern is
formed, thereby forming a resin film that is thicker than the lyophobic
pattern in an area where the lyophobic pattern is not formed; a mask
formation step of curing the resin film, to thus form on the processing
target surface a mask for covering an area except for the area to be
etched away; a lyophobic pattern removal step of removing the lyophobic
pattern from the processing target surface after performance of
processing pertaining to the mask formation step; an etching step of
performing etching the semiconductor wafer from the processing target
surface until the protective sheet becomes exposed on the processing
target surface, after processing pertaining to the lyophobic pattern
removal step; and a mask removal step of removing the mask from the
processing target surface after completion of processing pertaining to
the etching step.

3. A semiconductor chip with a resin adhesive layer manufacturing method
for manufacturing semiconductor chips having on rear surfaces resin
adhesive layers for die-bonding purpose by means of plasma dicing for
separating a semiconductor wafer, which has a plurality of semiconductor
devices on a circuit fabrication surface and which is affixed with a
protective sheet for protecting the circuit fabrication surface, into
respective semiconductor devices by means of etching using plasma
processing, the method comprising: a lyophobic pattern formation step of
printing a lyophobic liquid on scribe lines serving as borders between
semiconductor chips on a rear surface of the semiconductor wafer that is
another side of the circuit fabrication surface and a contour set along
an outer edge of the semiconductor wafer to a predetermined width,
thereby forming a lyophobic pattern; a resin film formation step of
supplying a liquid resin on the rear surface of the semiconductor wafer
on which the lyophobic pattern is formed, thereby forming a resin film
that is thicker than the lyophobic pattern in an area where the lyophobic
pattern is not formed; a resin adhesive layer formation step of
semi-curing the resin film, to thus form a resin adhesive layer; a
lyophobic pattern removal step of removing the lyophobic pattern from the
rear surface after performance of processing pertaining to the resin
adhesive layer formation step; and an etching step of etching, after
performance of processing pertaining to the lyophobic pattern removal
step, the semiconductor wafer from the rear surface while the resin
adhesive layer is taken as a mask until the protective sheet becomes
exposed on the rear surface.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a substrate processing method for
partially eliminating a substrate, like a semiconductor wafer, a
semiconductor chip manufacturing method to which the substrate processing
method is applied, and a resin-adhesive-layer-backed semiconductor chip
manufacturing method.

BACKGROUND ART

[0002] A semiconductor device to be mounted on a substrate of electronic
equipment is manufactured by means of slicing into pieces a semiconductor
chip made up of discrete semiconductor devices from a semiconductor
wafer, wherein integrated circuits are fabricated in the respective
discrete semiconductor devices in a wafer state. With a recent increase
in the degree of difficulty in handling a semiconductor chip resultant
from a decrease in thickness of the semiconductor chip, there has been
proposed plasma dicing for dicing a semiconductor wafer into pieces of
semiconductor chips by means of plasma etching.

[0003] Plasma dicing is to etch a semiconductor wafer by means of plasma
while the semiconductor wafer except for scribe lines showing grid-shaped
split positions is masked by means of a resist film, thereby cutting the
semiconductor wafer along the scribe lines. Therefore, plasma dicing
requires a step of making a mask over the semiconductor wafer. A mask has
heretofore been made by means of a photolithography (see Patent Document
1) for transferring a scribe line pattern by use of a photosensitive
material or a method (see Patent Document 2) for eliminating a scribe
line area on a mask layer formed over a surface of a semiconductor wafer
by irradiation of a laser beam to thereby make a mask.

[0006] However, the foregoing related art examples encounter a problem of
mask formation involving consumption of high cost. Specifically, the
photolithography technique is originally intended for a high precision
pattern, such as an integrated circuit and requires complicate steps and
expensive facilities, which inevitably entails a cost rise. Forming a
mask by use of a laser beam entails facility cost for laser beam
irradiation, which poses difficulty in forming a mask at low cost. The
problems pertaining to mask formation are not limited solely to plasma
dicing and are also true for various processing operations utilizing an
application of plasma etching; for instance, processing for making via
holes in a substrate, processing intended for a substrate for use with a
MEMS (Microelectromechanical System), and a substrate processing method
for fabricating integrated circuits on a transparent display panel, and
the like.

[0007] Accordingly, the present invention aims at providing a substrate
processing method that enables inexpensive formation of a mask for
etching using plasma processing, a semiconductor chip manufacturing
method utilizing an application of the substrate processing method, and a
resin-adhesive-layer-backed semiconductor chip manufacturing method.

Means for Solving the Problem

[0008] A substrate processing method of the present invention is directed
toward a substrate processing method for partially eliminating a
substrate by etching using plasma processing, the method comprising:

[0009] a lyophobic pattern formation step of printing, on a processing
target surface of the substrate, a lyophobic liquid to an area to be
etched away and a contour set along an outer edge of the substrate to a
predetermined width, thereby forming a lyophobic pattern;

[0010] a resin film formation step of supplying a liquid resin on the
processing target surface of the substrate on which the lyophobic pattern
is formed, thereby forming a resin film that is thicker than the
lyophobic pattern in an area where the lyophobic pattern is not formed;

[0011] a mask formation step of curing the resin film, to thus form on the
processing target surface a mask for covering an area except for the area
to be etched away;

[0012] a lyophobic pattern removal step of removing the lyophobic pattern
from the processing target surface after performance of processing
pertaining to the mask formation step;

[0013] an etching step of etching the substrate from the processing target
surface thereof by plasma processing after processing pertaining to the
lyophobic pattern removal step; and

[0014] a mask removal step of removing the mask from the processing target
surface after completion of processing pertaining to the etching step.

[0015] A semiconductor chip manufacturing method of the present invention
is directed toward a semiconductor chip manufacturing method for
separating a semiconductor wafer, which has a plurality of semiconductor
devices on a circuit fabrication surface and which is affixed with a
protective sheet for protecting the circuit fabrication surface, into
semiconductor chips made up of respective semiconductor devices by means
of etching using plasma processing, the method comprising:

[0016] a lyophobic pattern formation step of printing a lyophobic liquid
on scribe lines serving as borders between semiconductor chips on a
processing target surface of the semiconductor wafer that is another side
of the circuit fabrication surface and a contour set along an outer edge
of the semiconductor wafer to a predetermined width, thereby forming a
lyophobic pattern;

[0017] a resin film formation step of supplying a liquid resin on the
processing target surface of the semiconductor wafer on which the
lyophobic pattern is formed, thereby forming a resin film that is thicker
than the lyophobic pattern in an area where the lyophobic pattern is not
formed;

[0018] a mask formation step of curing the resin film, to thus form on the
processing target surface a mask for covering an area except for the area
to be etched away;

[0019] a lyophobic pattern removal step of removing the lyophobic pattern
from the processing target surface after performance of processing
pertaining to the mask formation step;

[0020] an etching step of performing etching the semiconductor wafer from
the processing target surface until the protective sheet becomes exposed
on the processing target surface, after processing pertaining to the
lyophobic pattern removal step; and

[0021] a mask removal step of removing the mask from the processing target
surface after completion of processing pertaining to the etching step.

[0022] A semiconductor chip with a resin adhesive layer manufacturing
method is directed toward a semiconductor chip with a resin adhesive
layer manufacturing method for manufacturing semiconductor chips having
on rear surfaces resin adhesive layers for die-bonding purpose by means
of plasma dicing for separating a semiconductor wafer, which has a
plurality of semiconductor devices on a circuit fabrication surface and
which is affixed with a protective sheet for protecting the circuit
fabrication surface, into respective semiconductor devices by means of
etching using plasma processing, the method comprising:

[0023] a lyophobic pattern formation step of printing a lyophobic liquid
on scribe lines serving as borders between semiconductor chips on a rear
surface of the semiconductor wafer that is another side of the circuit
fabrication surface and a contour set along an outer edge of the
semiconductor wafer to a predetermined width, thereby forming a lyophobic
pattern;

[0024] a resin film formation step of supplying a liquid resin on the rear
surface of the semiconductor wafer on which the lyophobic pattern is
formed, thereby forming a resin film that is thicker than the lyophobic
pattern in an area where the lyophobic pattern is not formed;

[0025] a resin adhesive layer formation step of semi-curing the resin
film, to thus form a resin adhesive layer;

[0026] a lyophobic pattern removal step of removing the lyophobic pattern
from the rear surface after performance of processing pertaining to the
resin adhesive layer formation step; and

[0027] an etching step of etching, after performance of processing
pertaining to the lyophobic pattern removal step, the semiconductor wafer
from the rear surface while the resin adhesive layer is taken as a mask
until the protective sheet becomes exposed on the rear surface.

ADVANTAGES OF THE INVENTION

[0028] According to the present invention, during mask formation
implemented by etching using plasma processing, there is adopted a method
including printing a lyophobic liquid in an area on the processing target
surface to be etched away and a contour set along an outer edge of the
substrate to a predetermined width, thereby forming a lyophobic pattern;
supplying a liquid resin on the processing target surface of the
substrate on which the lyophobic pattern is formed, thereby forming a
resin film that is thicker than the lyophobic pattern in an area where
the lyophobic pattern is not formed; and curing the resin film, to thus
form a mask that covers an area except the area to be etched. Thus, a
mask for etching using plasma processing can be formed at low cost
without use of a high-cost method, like photolithography.

[0029] Further, according to the present invention, during manufacture of
semiconductor chips for separating a semiconductor wafer into
semiconductor chips formed from respective semiconductor devices by means
of etching using plasma processing, there is adopted a method including
printing a lyophobic liquid on scribe lines serving as borders between
semiconductor chips on a rear surface of the semiconductor wafer and a
contour set along an outer edge of the semiconductor wafer to a
predetermined width, thereby forming a lyophobic pattern; supplying a
liquid resin on the processing target surface of the semiconductor wafer
on which the lyophobic pattern is formed, thereby forming a resin film
that is thicker than the lyophobic pattern in an area where the lyophobic
pattern is not formed; and curing the resin film, to thus form a mask
that covers an area except the area to be etched. Thus, a mask for
etching using plasma processing is formed at low cost, so that
semiconductor chips can be manufactured at low cost.

[0030] Moreover, according to the present invention, during manufacture of
semiconductor chips for separating a semiconductor wafer into
semiconductor chips with resin adhesive layers formed from respective
semiconductor devices by means of etching using plasma processing, there
is adopted a method including printing a lyophobic liquid on scribe lines
serving as borders between semiconductor chips on a rear surface of the
semiconductor wafer and a contour set along an outer edge of the
semiconductor wafer to a predetermined width, thereby forming a lyophobic
pattern; supplying a liquid resin on the rear surface of the
semiconductor wafer on which the lyophobic pattern is formed, thereby
forming a resin film that is thicker than the lyophobic pattern in an
area where the lyophobic pattern is not formed; and semi-curing the resin
film, to thus form a resin adhesive layer; and etching the rear surface
of the semiconductor wafer while the resin adhesive layer is taken as a
mask after removal of the lyophobic pattern from the rear surface. Thus,
a mask for etching using plasma processing is formed at low cost, and the
mask can be used as the resin adhesive layer for die-bonding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a flowchart showing a semiconductor chip manufacturing
method utilizing an application of a substrate processing method of a
first embodiment of the present invention.

[0032] FIGS. 2 (a) to (g) are explanatory process charts of the
semiconductor chip manufacturing method and a semiconductor chip boding
method that utilize the application of the substrate processing method of
the first embodiment of the present invention.

[0033] FIGS. 3 (a) to (d) are explanatory process charts of the
semiconductor chip manufacturing method and the semiconductor chip boding
method that utilize the application of the substrate processing method of
the first embodiment of the present invention.

[0034] FIG. 4 is a plan view of a semiconductor wafer that is an object of
the substrate processing method of the first embodiment of the present
invention.

[0035]FIG. 5 is a plan view of the semiconductor wafer that is an object
of the substrate processing method of the first embodiment of the present
invention.

[0036]FIG. 6 is an enlarged view of a lyophobic pattern of the substrate
processing method of the first embodiment of the present invention.

[0037] FIG. 7 is an enlarged cross sectional view of the semiconductor
wafer that is to be an object of the substrate processing method of the
first embodiment of the present invention.

[0038] FIGS. 8 (a) to (c) are explanatory views of resin coating performed
for making a mask under the substrate processing method of the first
embodiment of the present invention.

[0039] FIG. 9 is an enlarged view showing a liquid resin and the lyophobic
pattern employed in the substrate processing method of the first
embodiment of the present invention.

[0040]FIG. 10 is a cross sectional view of a resin layer and a mask of
the substrate processing method of the first embodiment of the present
invention.

[0041]FIG. 11 is a flowchart showing a resin-adhesive-layer-backed
semiconductor chip manufacturing method of a second embodiment of the
present invention.

[0042] FIGS. 12 (a) to (f) are explanatory process charts of the
resin-adhesive-layer-backed semiconductor chip manufacturing method and a
method for bonding a semiconductor chip with a resin adhesive layer of
the second embodiment of the present invention.

[0043] FIGS. 13 (a) to (d) are explanatory process charts of the
resin-adhesive-layer-backed semiconductor chip manufacturing method and
the method for bonding a semiconductor chip with a resin adhesive layer
of the second embodiment of the present invention.

[0044]FIG. 14 is an enlarged view of a lyophobic pattern of the
resin-adhesive-layer-backed semiconductor chip manufacturing method of
the second embodiment of the present invention.

[0045]FIG. 15 is an enlarged cross sectional view of a semiconductor
wafer that is to become an object of plasma dicing of the semiconductor
chip with a second resin adhesive layer manufacturing method of the
second embodiment of the present invention.

EMBODIMENTS FOR IMPLEMENTING THE INVENTION

First Embodiment

[0046] First, a lyophobic pattern and a mask of the present embodiment are
described. In the present embodiment, during mask formation that is
performed at the occasion of etching utilizing plasma processing for
separating a semiconductor wafer, a lyophobic pattern is formed by means
of a resin (a lyophobic agent) that exhibits a lyophobic property with
respect to a solvent included in a liquid resin that is to work as a
material making up a mask. Specifically, a lyophobic pattern is formed in
advance over an area of the semiconductor wafer, except for an area where
a mask is to be made, by use of the lyophobic agent. A liquid resin that
makes a mask is caused to adhere to only the area where the mask is to be
made. On the occasion of formation of the lyophobic pattern, a liquid (a
lyophobic liquid) made by dissolving the lyophobic agent in a solvent is
printed in a predetermined pattern by means of transfer printing, screen
printing, dispensing, inkjet printing, or the like. A solvent component
is volatized after printing, whereupon the lyophobic pattern is
completed.

[0047] A resin (resist) that will not be eliminated by a fluorine-based
gas plasma and that is easily removed (ashed) by means of oxygen or an
oxygen-contained gas plasma is used as a material making up the mask.
Hydrocarbon-based resins have been used as resins exhibiting these
properties. On the occasion of mask formation, a liquid resin made by
dissolving a resist in a solvent is applied over a processing target
surface of a substrate over which the lyophobic pattern has been formed,
by means of a method like dispensing, inkjet printing, and spin coating.
Since the lyophobic agent repels the solvent of the liquid resin applied
over the processing target surface, the liquid resin spreads over only an
area of the processing target surface except for the lyophobic pattern.
The solvent of the liquid resin is volatized in a baking step, thereby
letting the resist adhere the processing target surface. A mask patterned
by the lyophobic pattern is thereby completed.

[0048] The present invention adopting such a mask formation method
involves a requirement that the lyophobic agent used for making the
lyophobic pattern be a combination exhibiting a lyophobic property with
respect to the solvent included in the liquid resin used for mask
formation. In addition, a solvent capable of blending with a resin that
is to serve as a resist must be chosen as a solvent. In general, two
types of chemicals have properties of easily blending with each other as
SP values (solubility parameters) of the respective chemicals are more
analogous to each other and repelling each other as the SP values
increasingly differ from each other. Therefore, when the resist to be
used is any of the hydrocarbon-based resins (having an SP value of 7.0 to
8.0), any of saturated-hydrocarbon-based solvents having an SP value of
7.0 to 8.0 is chosen as a solvent.

[0049] In relation to a choice of a lyophobic agent and a solvent used
with a liquid resin, there are chosen substances corresponding to a
combination of substances having different SP values, preferably a
combination of substances whose SP values differ from each other by a
value of 1.0 or more. Therefore, if the solvent is any of
saturated-hydrocarbon-based solvents (having an SP value of 7.0 to 8.0),
any of acrylic resins (having an SP value of 9.2) or fluorine-based
resins (having an SP value of 3.6) can be used as a lyophobic agent.
Further, when any of saturated-hydrocarbon-based solvents having an SP
value of 8.0 is used, a silicone-based resin (having an SP value of 7.0)
can be used as a lyophobic agent. As mentioned above, a substance whose
SP value differs from an SP value of the solvent used for a liquid resin
by a value of 1.0 or more is used as a lyophobic agent, whereby a liquid
resin used for mask formation can be easily arranged on the processing
target surface except for the lyophobic pattern.

[0050] Mask formation using the lyophobic pattern requires a uniform
supply of a liquid resin over the area of the processing target surface
surrounded by the lyophobic pattern without occurrence of a
two-dimensional gap on a border between the lyophobic pattern and the
area. However, mere application of a liquid resin causes a problem caused
by a viscosity of the liquid resin, such as that described below, which
poses a difficulty in forming a mask having a good shape. Specifically,
when the viscosity of the liquid resin is high, a supplied liquid resin
attempts to gather together into as simple a shape as possible because of
surface tension. For this reason, the liquid resin hardly enters an
indentation of a corner on the processing target surface where the
lyophobic pattern has a cross. A two-dimensional void that is not
supplied with a resin tends to occur in only the indentation.

[0051] On the contrary, when the viscosity of the liquid resin is low, the
resin easily spreads in a wet fashion over the processing target surface
when supplied in a liquid state. However, during a stage where the
solvent component of the resin evaporates, to thus cure the resin, the
resin cannot maintain a desirable mask shape. Specifically, since a
concentration of a solid resin component of the liquid resin whose
viscosity is set to a low level is low, the resin changes in the course
of evaporation of the solvent in such a way that a two-dimensional shape
as well as a thicknesswise shape of the resin contract. For this reason,
in a state where the liquid resin is supplied by application, the resin
remains uniformly spread in a wet fashion over the area surrounded by the
lyophobic pattern. However, when the resin becomes cured as a result of
evaporation of the solvent, the two-dimensional shape of the resin
becomes contracted. Therefore, a two-dimensional void devoid of a resin
occurs on the border between the lyophobic pattern and the area in the
same way as mentioned previously.

[0052] Such a failure in the shape of the mask attributable to the
viscosity of the liquid resin is ascribable to surface tension of the
resin when the resin has a high viscosity and contractive deformation
resultant from evaporation of the solvent when the resin has a low
viscosity. Therefore, it is extremely difficult to determine an
appropriate viscosity range that enables prevention of occurrence of such
a failure in shape. Accordingly, in the present embodiment, two types of
liquids having different viscosity levels are prepared in a process of a
mask being formed from a liquid resin as will be described below, and the
liquids are supplied in two steps. Specifically, prior to supplying a
high viscosity resin (a first liquid) including a resin component, which
is to make a mask, in a high concentration, a low viscosity resin (a
second liquid) that exhibits a viscosity lower than that of the high
viscosity resin is first supplied. The low viscosity resin is thus caused
to spread uniformly in a wet fashion within an area surrounded by the
lyophobic pattern. Next, the high viscosity resin is supplied, to thus
assure a quantity of resin component required to form a mask.

[0053] The substrate processing method is now described by reference to
the flowchart of FIG. 1 and explanatory process charts of FIGS. 2 and 3.
The substrate processing method is to partially eliminate a material
making up the substrate through performance of etching using plasma
processing. Plasma dicing is hereinbelow provided as example substrate
processing; in other words, a semiconductor wafer separated into a
plurality of semiconductor devices by means of scribe lines is taken as a
substrate, and the scribe lines are partially eliminated by means of
etching using a plasma, thereby separating the semiconductor wafer into
discrete semiconductor chips. The first embodiment, in a word, shows a
semiconductor chip manufacturing method for separating a semiconductor
wafer, which has a plurality of semiconductor devices on a circuit
fabrication surface and a protective sheet for protecting the circuit
fabrication surface affixed to the circuit fabrication surface, into
semiconductor chips made up of respective semiconductor devices, by means
of etching using plasma processing.

[0054] In FIG. 1, a lyophobic pattern is first made over a semiconductor
wafer 1 serving as a substrate (ST1). As shown in FIG. 2(a), a plurality
of semiconductor chips including integrated circuits (semiconductor
devices) are fabricated on the semiconductor wafer 1. A protective sheet
2 for protecting the integrated circuits is affixed to a circuit
fabrication surface 1a of the semiconductor wafer 1 where the integrated
circuits are fabricated. A rear surface 1b that is the other side of the
circuit fabrication surface 1a is made thin to a thickness of 100
micrometers or less by means of removing a surface layer in a thinning
step, which is a preceding step, through performance of mechanical
grinding.

[0055] Next, as shown in FIG. 2(b), a lyophobic pattern is formed, on the
rear surface 1b (corresponding to the processing target surface of the
substrate to be etched) of the semiconductor wafer 1, along grid lines
(corresponding to areas to be etched away) corresponding to scribe lines
1c (see FIG. 4) that separate the semiconductor wafer 1 into respective
semiconductor chips 1e and along a contour [see FIG. 2(a) and a lyophobic
film 3e shown in FIG. 5] set to a predetermined width along an outer edge
of the semiconductor wafer 1 (a lyophobic pattern formation step). In
addition to being formed along the grid lines corresponding to the scribe
lines 1c (see FIG. 4), the lyophobic pattern is formed along the contour
of the outer edge of the semiconductor wafer 1. The lyophobic pattern
formed along the contour is intended to prevent the liquid resin from
running over the outer edge of the semiconductor wafer 1 to thereby fall
from the wafer, which would otherwise occur when the liquid resin is
applied after formation of the lyophobic pattern. The lyophobic pattern
formation step includes a print step of printing a lyophobic liquid in a
predetermined pattern on the processing target surface and a baking step
of letting a solvent component of the printed lyophobic liquid evaporate,
to thus cause the lyophobic agent to adhere to the processing target
surface, to thus produce the lyophobic film 3.

[0056] In the print step, a method that enables linear supply of a
lyophobic liquid, such as transfer printing, screen printing, dispensing,
and inkjet printing, is employed. Specifically, as shown in FIG. 6, a
liquid that is to form the lyophobic film 3 is printed in a grid shape of
the scribe lines 1c to a print width "b" (about 20 micrometers) within a
range of the width of each of the scribe lines 1c set in consideration of
a dicing margin having a separation width B (about 50 micrometers to 60
micrometers). Moreover, a liquid that is to form a lyophobic film 3e is
printed in a circumferential pattern along the contour that is set along
the outer edge of the semiconductor wafer 1 to a predetermined width
corresponding to the print width "b." At this time, an essential
requirement for a widthwise position of the lyophobic film 3 is that the
lyophobic film 3 should fall within a range of the separation width B of
each of the scribe lines 1c. Therefore, a widthwise positional error of
about ±20 micrometers is allowed. A widthwise edge 3a on either side
of the lyophobic film 3 does not require a high degree of linear
accuracy. Even when the edge exhibits a wavelike shape to some extent,
the edges do not cause any problem. Likewise, the lyophobic film 3e does
not require a widthwise positional accuracy, either, and is allowed to
exhibit a wavelike shape to some extent.

[0057] The lyophobic pattern formed along a periphery of the outer edge of
the semiconductor wafer 1 is now described in detail. As shown in FIG. 6,
in relation to the scribe lines 1c (FIG. 4) that separate normal
semiconductor chips 1e in the semiconductor wafer 1, the lyophobic film 3
is orderly printed in a grid shape. On the contrary, the lyophobic film 3
is not always printed along the grid lines shown in FIG. 4 in the
vicinity of a contour of the outer edge of the semiconductor wafer 1.
Depending on a size of squares surrounded by inner lyophobic films 3 and
the lyophobic film 3e of the contour, printing the lyophobic films 3 is
omitted. Specifically, when the lyophobic pattern is formed by printing
the lyophobic films 3 along the grid lines and when areas of respective
squares surrounded by the grid-like lyophobic films 3 and the lyophobic
film 3e of the outer edge are too small to efficiently apply a resin,
printing the lyophobic films 3 along the grid lines corresponding to
borders between the current square and adjoining squares is omitted to
unite the square with the adjoining square.

[0058] In FIG. 5, in relation to much of outer edge squares 1R(1) to 1R(9)
defined by areas surrounded by the lyophobic film 3e formed along the
contour of the semiconductor wafer 1 and the lyophobic films 3 printed in
grid lines, some of the lyophobic films 3 corresponding to the grid lines
are omitted, and adjoining two squares unite with each other, thereby
forming one square. As a result, areas [A1] to [A9] of the respective
outer edge squares 1R(1) to 1R(9) do not much differ from an area [A] of
the normal semiconductor chip 1e separated by the scribe lines 1c.
Occurrence of excessive variations in required quantity of liquid resin
applied, which will be described later, can be prevented. Alternatively,
it is also possible to calculate the area [A] of the semiconductor chip
1e and the respective areas [A1] to [A9] of the outer edge squares 1R(1)
to 1R(9) in advance as numerical data and store the data as application
quantity data showing an appropriate quantity of resin applied to each
square.

[0059] After the print step, the semiconductor wafer 1 is sent to the
baking step, where the wafer is heated to a temperature of the order of
40 degrees centigrade to 50 degrees centigrade, whereby the lyophobic
films 3 whose lyophobic agent has adhered to the rear surface 1b are
formed. As shown in FIG. 7, a thickness t1 of the lyophobic films 3 comes
to 0.1 micrometers to 2 micrometers. When processing pertaining to the
baking step is performed in a vacuum, a baking temperature can be
reduced, so that occurrence of an increase in print width "b" can be
prevented. If the solvent component evaporates during the print step,
there will be no need to perform processing pertaining to the baking
step.

[0060] The semiconductor wafer 1 on which the lyophobic pattern has been
formed as mentioned above comes to an objective of application of a
liquid resin for mask formation. As mentioned previously, the resin is
applied in two steps; namely, the low viscosity resin (the second liquid)
exhibiting superior wettability is previously applied in order to assure
an appropriate spread of a high viscosity resin within the areas
surrounded by the lyophobic films 3 before applying the high viscosity
resin (the first liquid) including a resin, which is to make up a mask,
in a solvent in a high concentration.

[0061] Any of hydrocarbon resins, which are not eliminated by plasma
etching performed for the purpose of eliminating silicon--a material of
the semiconductor wafer 1--and which can be easily removed by plasma
ashing intended for removing a mask later, is used for the resin (resist)
included in the first liquid that is the high viscosity resin. A liquid
solution made by dissolving the resin in a saturated-hydrocarbon-based
solvent is used as the first liquid. A composition of the first liquid is
set such that a resin serving as solute assumes 40 to 80 percent content
and that a solvent assumes 60 to 20 percent content. It is preferable to
set the resin content so as to fall within a range from 40 to 50
percents.

[0062] The second liquid is set such that a resin (identical with the
resin included in the first liquid) serving as solute assumes 0 to 40
percent content and that a solvent assumes 100 to 70 percent content. It
is preferable to set the resin content so as to fall within a range from
10 to 20 percents. A purpose of application of the second liquid is to
spread the second liquid in a wet fashion over the rear surface 1b in
order to assure an appropriate spread of the high viscosity resin that is
the first liquid to be applied later. Therefore, the second liquid does
not always need to include a resin as solute. As indicated by the
composition mentioned above, the first liquid may also be formed from 0
percent solute content and 100 percent solvent content.

[0063] When the second liquid includes a resin, the second liquid is a low
concentration, low viscosity resin including a resin content that is
lower than that of the first liquid. When the second liquid does not
include a resin, the second liquid is made of only a solvent. In any
case, the second liquid is lower than the first liquid in terms of
viscosity. The second liquid exhibits superior wettability required to
assure an appropriate spread of the first liquid to be applied later.

[0064] Specifically, under the substrate processing method described in
connection with the embodiment, two types of liquids are prepared;
namely, the first liquid including at least a solvent and a resin, and
the second liquid whose viscosity is lower than that of the first liquid.
Example configurations for making the viscosity of the second liquid
lower than the viscosity of the first liquid include a first
configuration for making the second liquid from solely a solvent and a
second configuration for making the concentration of the resin included
in the second liquid lower than the concentration of the resin included
in the first liquid. In the first and second configurations, the second
liquid includes the same solvent as that of the first liquid. In the
second configuration, the second liquid includes the same resin as that
of the first liquid, and the concentration of the resin included in the
second liquid is lower than the concentration of the resin included in
the first liquid.

[0065] For convenience's sake, a single type of solvent is used for the
first liquid and the second liquid. However, the solvent of the first
liquid does not always need to be identical with the solvent of the
second liquid. A solvent of another type can also be used for the second
liquid, so long as the solvent has a property of being dissolved in the
first liquid. Likewise, example configurations for making the viscosity
of the second liquid lower than the viscosity of the first liquid include
a third configuration for forming the second liquid from solely a solvent
and a fourth configuration for making the concentration of the resin
included in the second liquid lower than the concentration of the resin
included in the first liquid. In the third and fourth configurations, the
solvent of the second liquid differs in type from the solvent of the
first liquid, and the solvent has a property of being dissolved in the
first liquid. In the fourth configuration, the resin included in the
second liquid is identical with the resin included in the first liquid.
The concentration of the resin included in the second liquid is lower
than the concentration of the resin included in the first liquid.

[0066] The thus-prepared first and second liquids are supplied, in
sequence of the second liquid and the first liquid, to the semiconductor
wafer 1 on which the lyophobic pattern has been formed. An explanation is
now given to a case where a low viscosity resin including a resin in a
low concentration is used as the second liquid. First, as shown in FIG.
1, the low viscosity resin is applied (ST2). Specifically, as shown in
FIG. 2(b), a low viscosity resin 4a (the second liquid) for the purpose
of mask formation is supplied to the rear surface 1b that is the
processing target surface of the semiconductor wafer 1 on which the
lyophobic pattern is formed from the lyophobic films 3.

[0067]FIG. 8(a) shows a state in which a dispense nozzle 5A applies the
low viscosity resin 4a. As mentioned previously, the low viscosity resin
4a squirted from the dispense nozzle 5A to a center position in an area R
surrounded by the lyophobic films 3 on the rear surface 1b spreads in a
wet fashion toward a periphery within the area R along the rear surface
1b. The low viscosity resin 4a spread in a wet fashion is repelled by
surfaces of the lyophobic films 3 exhibiting a lyophobic property, to
thus adhere to only the area devoid of the lyophobic films 3. At this
time, the low viscosity resin 4a has low viscosity and exhibits superior
wettability and, hence, reliably advances to positions adjacent to
borders D between the lyophobic films 3 formed in a grid shape and the
area R. Further, the low viscosity resin 4a also advances to indentations
of corners C where the lyophobic films 3 cross each other without causing
gaps.

[0068] The high viscosity resin is now applied (ST3). As shown in FIG.
2(c), in addition to the low viscosity resin 4a, a high viscosity resin
4b (the first liquid) including a resin for mask formation in a high
concentration is applied to the rear surface 1b of the semiconductor
wafer 1 over which the low viscosity resin 4a has already been applied.
Specifically, as shown in FIG. 8(b), a dispense nozzle 5B squirts the
high viscosity resin 4b to the center of the area R on the rear surface
1b that is surrounded by the lyophobic films 3 and where the low
viscosity resin 4a has already been applied. At this time, since a
coating film of the low viscosity resin 4a that is to be dissolved in the
high viscosity resin 4b has already been formed over the entirety of the
area R, the squirted high viscosity resin 4b spreads toward the periphery
within the area R while being dissolved in the low viscosity resin 4a and
also guided by the low viscosity resin 4a. During the course of spread of
the high viscosity resin 4b, the concentration of the resin in the low
viscosity resin 4a and the concentration of the resin in the high
viscosity resin 4b become uniform.

[0069] The low viscosity resin 4a and the high viscosity resin 4b are
thereby mixed together, whereby a resin film 4 having a uniform
concentration of resin is produced. The resin film 4 is at this time
repelled by the surface of the lyophobic films 3 exhibiting a lyophobic
property, thereby adhering to only areas devoid of the lyophobic films 3
and advancing to positions where the films become close to the borders D.
Further, the resin film enters the indentations of the corners C without
causing gaps. As shown in FIG. 8(c), the resin film 4 having a thickness
t2 (see FIG. 10) that is larger than the thickness t1 of the lyophobic
films 3 (see FIG. 7) is formed in the area R surrounded by the lyophobic
films 3. It is preferable that a composition of the resin film 4 achieved
when the low viscosity resin 4a and the high viscosity resin 4b are
completely mixed together should include 30% or more and, desirably,
about 40% of a resin serving as solute. By adoption of such a resin
content, the rein film 4 holds itself on the rear surface 1b within the
area R surrounded by the lyophobic films 3 in the course of the resin
film 4 being heated, to thus evaporate the solvent. Therefore, the resin
film 4 can sustain its shape in an applied state without causing
contraction of a two-dimensional shape.

[0070] Specifically, in the steps (ST2) and (ST3) where the previously
prepared low viscosity resin 4a serving as the first liquid and the high
viscosity resin 4b serving as the second liquid are supplied to the rear
surface 1b, which is the processing target surface of the semiconductor
wafer 1 on which the lyophobic pattern is formed, in sequence of the high
viscosity resin 4b serving as the second liquid and the low viscosity
resin 4a serving as the first liquid. The resin film 4 whose thickness is
larger than that of the lyophobic pattern is thereby formed in the area R
that is surrounded by the lyophobic films 3 and where the lyophobic
pattern is not formed (a resin film formation step).

[0071] Since the lyophobic film 3e having the same lyophobic property as
that of the lyophobic films 3 is formed along the contour of the
semiconductor wafer 1 set along the outer edge of the semiconductor wafer
1 to a predetermined width, on the occasion of application of the low
viscosity resin 4a and the high viscosity resin 4b, the low viscosity
resin 4a and the high viscosity resin 4b squirted from the respective
dispense nozzles 5A and 5B to the contour of the semiconductor wafer 1
are repelled by the lyophobic film 3e. Therefore, it is possible to
prevent the low viscosity resin 4a and the high viscosity resin 4b from
hanging and falling from the outer edge of the semiconductor wafer 1,
which would otherwise occur when the lyophobic film 3e is not present,
and also prevent staining of the wafer table, which would otherwise be
cause by a drop of the resin.

[0072] In relation to application of the low viscosity resin 4a from the
dispense nozzle 5A and application of the high viscosity resin 4b from
the dispense nozzle 5B, a quantity of resin squirted from the dispense
nozzle 5A and a quantity of resin squirted from the dispense nozzle 5B
may also be controlled according to the area of the square surrounded by
the lyophobic films 3. Specifically, as has been described by reference
to FIG. 5, the quantity of resin squirted from the dispense nozzle 5A and
the quantity of resin squired from the dispense nozzle 5B are controlled
according to application quantity data that specify for each square an
appropriate quantity of resin applied, in association with the area [A]
of the semiconductor chip 1e and the areas [A1] to [A9] of the outer edge
squares 1R(1) to 1R(9). A proportion of the quantity of the low viscosity
resin 4a applied to the quantity of the high viscosity resin 4b applied
is set for each square in such a way that the quantity of the high
viscosity resin 4b applied falls within a range from two to five,
provided that the quantity of the low viscosity resin 4a applied is taken
as one.

[0073] FIG. 9 shows, in an enlarged manner, a state of a contact between
the lyophobic films 3 and the resin film 4 achieved after the resin film
formation step. Although the edges 3a on both widthwise edges of each of
the lyophobic films 3 assume a minute wavelike shape (a saw-toothed
shape), a contour 4c of the resin film 4 (illustrated by broken lines in
FIG. 9) remaining in contact with the edges 3a forms a
substantially-linear, smooth line. The reason for this is that the resin
film 4 exhibits surface tension in a liquid state and also a property of
being impervious to following minute irregularities of the respective
edges 3a because of action of surface tension. The property is very
advantageous in view of formation of a mask having smooth edges. When the
resin film 4 having the smooth contour 4c is treated in the subsequent
baking step, a mask having edges (smooth edges) corresponding to the
contour 4c is formed.

[0074] Subsequently, the thus-applied resin is dried (ST4). The
semiconductor wafer 1 on which the resin film 4 is formed is again sent
to the baking step, where the semiconductor wafer 1 is heated to a
temperature ranging from 40 degrees centigrade to 70 degrees centigrade.
As shown in FIG. 2(d), the solvent of the resin film 4 is vaporized,
thereby forming, on the rear surface 1b that is the processing target
surface (a mask formation step), a mask 4* that covers an area of the
semiconductor wafer 1 except for the area (the area of the lyophobic
films 3 set along the scribe lines 1c) to be etched away by plasma
processing (the mask formation step).

[0075]FIG. 10 is a cross sectional view of the resin film and the mask.
During the mask formation step, the solvent evaporates from the resin
film 4, and a thickness t3 of the mask therefore becomes smaller than the
thickness t2 of the resin film. For this reason, the thickness t3 of the
mask is adjusted by adjustment of the thickness t2 of the resin film 4;
namely, setting the resin content in the low viscosity resin 4a and the
resin content in the high viscosity resin 4b and controlling the quantity
of the low viscosity resin 4a applied and the quantity of the high
viscosity resin 4b applied. The required thickness t3 of the mask is
determined in consideration of etch resistance and an ashing time. In the
present embodiment, a preferred value of the thickness t3 ranges from 5
micrometers to 20 micrometers. A relationship (a contraction factor)
between the thickness t2 and the thickness t3 can be determined by a
test, or the like. Accordingly, the thickness t2 of the resin film 4
required to obtain the required thickness t3 of the mask is determined
from the contraction factor and the thickness t3. When the thickness t2
is determined, the resin content of the low viscosity resin 4a, the
quantity of low viscosity resin 4a applied, the resin content of the high
viscosity resin 4b, and the quantity of high viscosity resin 4b applied,
all of which are required to achieve the thickness t2, can be determined
by calculation.

[0076] After the mask formation step, the lyophobic pattern is removed as
shown in FIG. 2(e) (ST5). Specifically, there is performed processing for
dissolving the lyophobic pattern formed from the lyophobic films 3 by
means of a solvent, to thus eliminate the lyophobic pattern from the rear
surface 1b that is the processing target surface (a lyophobic pattern
removal step). Processing is performed by supplying a solvent, such as
ketones, polyalcohols, cyclic ethers, lactones, and esters, to the rear
surface 1b on which the mask has already been formed, thereby dissolving
the resin component of the lyophobic films 3 and eliminating the
thus-dissolved films along with the solvent. A solvent that differs
little from the substance used for the lyophobic films 3 in terms of an
SP value is chosen as the solvent to be used this time. Dipping, spin
etching, spraying, or the like, can be used as a method for supplying the
solvent to the rear surface 1b, to thus remove the lyophobic films 3.

[0077] Processing pertaining to the lyophobic pattern removal step can
also be performed by means of plasma etching using an oxygen gas plasma.
Specifically, the semiconductor wafer 1 having undergone processing
pertaining to the mask formation step is exposed in such a way that the
rear surface 1b is irradiated with the oxygen gas plasma. The lyophobic
films 3 and the mask 4*, which each are organic substances, are
incinerated by ashing action of the oxygen gas plasma, to thus be
removed. However, the thickness t3 of the mask 4* is sufficiently larger
than the thickness t1 of the lyophobic films 3. Therefore, even after the
lyophobic films 3 have been removed by ashing, the mask 4* still remains
in a sufficient thickness on the rear surface 1b. Thus, the mask 4* can
fulfill its function as a mask for etching using plasma.

[0078] After the lyophobic pattern removal step, the semiconductor wafer 1
that is a substrate is subjected to plasma etching (ST6). Specifically,
the semiconductor wafer 1 is etched for dicing by means of plasma
processing from the rear surface 1b that is the processing target surface
of the semiconductor wafer 1, until the protective sheet 2 becomes
uncovered (an etching step). The semiconductor wafer 1 is sent to a
plasma processing apparatus, where the rear surface 1b of the
semiconductor wafer 1 is irradiated with a fluorine-based gas plasma P,
such as SF6, (FIG. 2(f)). A portion of the rear surface 1 b of the
semiconductor wafer 1, which is not covered with the mask 4* and exposed
to the plasma P, is removed by etching action of the plasma P, whereby an
etching trench 1d is formed. As a result of the etching trench 1d
penetrating through an entire thickness of the semiconductor wafer 1,
whereupon the semiconductor wafer 1 is separated into discrete
semiconductor chips 1e as shown in FIG. 2(f).

[0079] During etching using the plasma P, the mask 4* having smooth edges
is formed. Consequently, a diced edge of each of the separated discrete
semiconductor chips 1e achieves a smooth, irregularity-free cut surface.
Therefore, it is possible to prevent occurrence of a defect that would
deteriorate reliability of a semiconductor chip; in other words, a
problem that is likely to arise when a cut surface has a rough shape, or
minute cracks attributable to concentration of stress on minute
irregularities.

[0080] The mask 4* is then removed (ST7). The semiconductor wafer 1 having
finished undergoing processing pertaining to the etching step is
subjected to processing for removing the mask 4* from the rear surface 1b
that is the target processing surface (a mask removal step). Mask removal
is performed by means of ashing for incinerating and removing the resin
film 4 including a hydrocarbon-based resin as a component by use of an
oxygen gas plasma. As a matter of course, a method for mechanically
exfoliating the mask 4* from the rear surface 1b or a wet mask removal
method using a chemical can also be used during mask removal. The
semiconductor wafer 1 thereby enters a state in which the discrete
semiconductor chips 1e are individually affixed to the protective sheet 2
as shown in FIG. 2(g).

[0081] Subsequently, a die-bonding sheet 11 is affixed to the surface from
which the mask 4* has already been removed (ST8). As shown in FIG. 3(a),
the semiconductor wafer 1 from which the mask has already been removed;
namely, the plurality of semiconductor chips 1e that each have the
circuit fabrication surfaces 1a adhesively held by the protective sheet
2, is transferred while the respective rear surfaces 1b of the respective
semiconductor chips 1e are affixed to the die-bonding sheet 11. The
die-bonding sheet 11 is stretched to an annular wafer ring 12a, to thus
make up a wafer jig 12.

[0082] The protective sheet 2 is now removed (ST9). Specifically, the
protective sheet 2 is peeled off from the semiconductor chips 1e affixed
to the die-bonding sheet 11. As shown in FIG. 3(b), the discrete
semiconductor chips 1e exposed with their circuit fabrication surfaces 1e
oriented upward are held, through the respective rear surfaces 1b, by the
die-bonding sheet 11, thereby completing a semiconductor chip aggregate
10. The semiconductor chip aggregate 10 is sent in this state to a die
bonder. As shown in FIG. 3(c), the wafer ring 12a is held by a wafer hold
mechanism 13 of the die bonder, whereby the discrete semiconductor chip
1e enters a state in which the chip can be picked up.

[0083] On the occasion of the picking-up of the semiconductor chip 1e, a
bonding tool 14 and an ejector 15 are positioned to the semiconductor
chip 1e that is to be picked up. An ejector pin 16 provided on the
ejector 15 pushes the semiconductor chip 1e to be taken out from below,
and the bonding tool 14 picks up and holds the semiconductor chip 1e. The
bonding tool 14 has built-in heating means, and the semiconductor chip 1e
is heated to a predetermined temperature as a result of being held by the
bonding tool 14.

[0084] The bonding tool 14 that holds the thus-picked-up semiconductor
chip 1e travels to a position above a heating support 17 that holds a
substrate 18 to be bonded. A die-bonding adhesive 19 is applied over the
substrate 18 in advance, and the substrate 18 is also heated in advance
to a predetermined temperature by a heating mechanism (omitted from the
drawings) provided in the heating support 17. The semiconductor chip 1e
is aligned to a bonding position, and the bonding tool 14 is lowered,
thereby placing the semiconductor chip 1e on an upper surface of the
substrate 18 by way of the adhesive 19. Next, the bonding tool 14 presses
the semiconductor chip 1e against the substrate 18 under predetermined
applied pressure. Thermosetting reaction of the adhesive 19 proceeds as a
result of the substrate being held in this state for a predetermined
period of time. The semiconductor chip 1e is bonded to the substrate 18
by means of the thermosetting adhesive 19.

[0085] As mentioned above, in the plasma dicing described in connection
with the first embodiment, the following method is employed during mask
formation implemented by etching using plasma processing. Namely, the
method includes printing the lyophobic liquid on an area to be etched,
thereby forming the lyophobic pattern from the lyophobic films 3;
preparing two types of liquids; namely, the first liquid including at
least a solvent and a resin, and the second liquid whose viscosity is
lower than that of the first liquid; supplying the liquids, in descending
sequence of the second liquid and the first liquid, to the processing
target surface of the substrate over which the lyophobic pattern is
already formed, thereby forming the resin film 4 that is thicker than the
lyophobic pattern on the area where the lyophobic pattern is not formed;
and processing the semiconductor wafer over which the resin film 4 is
formed in the baking step, thereby forming the mask 4* that covers an
area of the semiconductor wafer except the area to be etched.

[0086] The lyophobic pattern produced under the foregoing method does not
need a high degree of positional accuracy and shape accuracy. Therefore,
the mask can be formed at low cost by means of the existing technique
using simple, in expensive facilities. Therefore, a mask for use in
etching using plasma processing can be formed at low cost without use of
a high-cost method, like photolithography and laser irradiation.

[0087] There is employed the method for applying two types of liquids;
namely, the first liquid including a solvent and a resin and the second
liquid whose viscosity is lower than that of the first viscosity, in
predetermined sequence, to thus form the resin film 4 for mask formation.
As a result, it is possible to effectively prevent occurrence of the
following problems, which would otherwise be likely to arise during
formation of a mask using a lyophobic pattern. Specifically, when a high
viscosity liquid resin is used, wet-spreading of the resin is hindered by
surface tension of the resin, thereby posing difficulty in letting the
resin enter the corners of the lyophobic pattern without casing gaps.
Thus, it is difficult to form a mask assuming an appropriate shape. When
a low viscosity liquid resin is used, superior wettability is achieved in
an applied state, and uniform application of the resin is possible.
However, occurrence of contractive deformation of a resin film, which
would otherwise be caused by evaporation of the solvent in the baking
step subsequent to resin application, is unavoidable, thereby likewise
posing difficulty in forming a mask having an appropriate shape.

[0088] On the contrary, there is adopted the method for using two types of
liquids and first supplying the second liquid and the first liquid. As a
result, the second liquid can be uniformly spread in a wet fashion within
an area surrounded by the lyophobic pattern. Next, the first liquid, or
the high viscosity resin, is supplied, whereby the first liquid can be
well spread in a wet fashion while being guided in the second liquid that
has already been applied. Therefore, the problem is dissolved, and the
resin film 4 for mask formation can be formed in a superior shape.

Second Embodiment

[0089] A second embodiment of the present invention relates to a
semiconductor chip manufacturing method utilizing an application of the
substrate processing method described in connection with the first
embodiment. A resin adhesive layer used when the discrete semiconductor
chips formed by separating the semiconductor chips are bonded is caused
to act as a mask required during etching operation using plasma
processing for separating the semiconductor wafer. In FIGS. 12 through
15, elements having configurations similar to those of their counterparts
described in connection with the first embodiment are assigned the same
reference numerals, and different reference numerals are assigned to
solely element having different configurations, to thus be distinguished.

[0090] First, a lyophobic pattern and a resin adhesive layer of the
present embodiment are described. In the present embodiment, a lyophobic
pattern is formed from a resin (a lyophobic agent) that exhibits a
lyophobic property against a solvent included in a liquid resin which is
to act as a material for making up a resin adhesive layer. Specifically,
the lyophobic pattern is formed, in advance, from a lyophobic agent in an
area except for an area on the semiconductor wafer where the resin
adhesive layer is formed. The liquid resin making up the resin adhesive
layer is caused to adhere to solely the area where the resin adhesive
layer is to be formed. On the occasion of formation of the lyophobic
pattern, a liquid (a lyophobic liquid) made by dissolving a lyophobic
agent in a solvent is printed in a predetermined pattern by means of
transfer printing, screen printing, dispensing, inkjet printing, or the
like. A solvent component is volatized after printing, whereupon the
lyophobic pattern is completed.

[0091] Thermosetting resins, such as epoxy-based resins, are used as a
resin making up a resin adhesive layer. On the occasion of formation of a
resin adhesive layer, a liquid resin made by dissolving a thermosetting
resin in a solvent is applied over the processing target surface of the
substrate over which the lyophobic pattern is formed, by means of a
method, like dispensing, inkjet printing, and spin-coating. Since the
solvent of the liquid resin applied over the processing target surface is
repelled by the lyophobic agent, the liquid resin spreads over only an
area of the processing target surface except for the lyophobic pattern.
The substrate over which the liquid resin is applied is heated, thereby
vaporizing the solvent. Further, the thermosetting resin is semi-cured,
whereby a resin adhesive layer patterned by the lyophobic pattern is
produced.

[0092] In the present invention adopting such a resin adhesive layer
formation method, the lyophobic agent used for the lyophobic pattern must
correspond to a combination of lyophobic agents that exhibit a lyophobic
property against the solvent included in the liquid resin used for
forming a resin adhesive layer. In addition, a solvent that is dissolved
in a thermosetting resin must be chosen. Accordingly, when a resin to be
used is any of epoxy-based thermosetting resins (having an SP value of
10.9), any of alcohol-based solvents having an SP value ranging from 10.0
to 11.9 is chosen as a solvent. Acrylic resins (having an SP value of
9.2), silicone-based resins (having an SP value of 7.0), and
fluorine-based resins (having an SP value of 3.6) can be used as a
lyophobic agent in this case.

[0093] Even in the second embodiment, during the course of the resin
adhesive layer being formed from liquid resins, two types of liquids
having different viscosity levels are prepared, and the liquids are
supplied in two steps in the same manner as in the first embodiment.
Specifically, a low viscosity resin (the second liquid) whose viscosity
is lower than a high viscosity resin is first supplied before supplying
the high viscosity resin (the first liquid) including a resin component
which is to make up the resin adhesive layer in a high concentration. The
low viscosity resin is uniformly spread in a wet fashion within the area
surrounded by the lyophobic pattern, and the high viscosity resin is then
supplied, thereby assuring a quantity of resin component required to form
a resin adhesive layer.

[0094] A resin-adhesive-layer-backed semiconductor chip manufacturing
method is now described by reference to the drawings; namely, a flowchart
of FIG. 11 and explanatory process charts of FIGS. 12 and 13. In FIG. 11,
a lyophobic pattern is first made over the semiconductor wafer 1 serving
as a substrate (ST11). As shown in FIG. 12(a), a plurality of
semiconductor chips including integrated circuits (semiconductor devices)
are fabricated on the semiconductor wafer 1. The protective sheet 2 for
protecting the integrated circuits is affixed to the circuit fabrication
surface 1a of the semiconductor wafer 1 where the integrated circuits are
fabricated. The rear surface 1b that is the other side of the circuit
fabrication surface 1a is made thin to a thickness of 100 micrometers or
less by means of removing a surface layer in a thinning step, which is a
preceding step, through performance of mechanical grinding.

[0095] Next, as shown in FIG. 12(b), a lyophobic pattern is formed, on the
rear surface 1b (corresponding to the processing target surface of the
substrate to be etched in the substrate), along the grid lines
(corresponding to areas to be etched away) corresponding to the scribe
lines 1c (see FIG. 4) that separate the semiconductor wafer 1 into the
respective semiconductor chips 1e and along the contour [see FIG. 2(a)
and the lyophobic film 3e shown in FIG. 5] set to a predetermined width
along the outer edge of the semiconductor wafer 1 (the lyophobic pattern
formation step). In addition to being formed along the grid lines
corresponding to the scribe lines 1c (see FIG. 4), the lyophobic pattern
is formed along the contour of the semiconductor wafer 1. The lyophobic
pattern formed along the contour is intended to prevent the liquid resin
from running over the outer edge of the semiconductor wafer 1 to thereby
fall from the wafer, which would otherwise occur when the liquid resin is
applied after formation of the lyophobic pattern. The lyophobic pattern
formation step is analogous to that described in connection with the
first embodiment, and hence its detailed explanation is omitted here for
brevity.

[0096] The semiconductor wafer 1 on which the lyophobic pattern has been
formed as mentioned above comes to an objective of application of a
liquid resin for making a resin adhesive layer. As mentioned previously,
the resin is applied in two steps; namely, the low viscosity resin (the
second liquid) exhibiting superior wettability is applied in advance in
order to assure an appropriate spread of the high viscosity resin within
the areas surrounded by the lyophobic films 3 before applying the high
viscosity resin (the first liquid) including a resin, which is to make up
a mask, in a solvent in a high concentration.

[0097] Any of thermosetting resins, such as epoxy-based resins, is used
for the resin to be included in the first liquid that is the high
viscosity resin. A solution made by dissolving the thermosetting resin in
an alcohol-based solvent is used as the first liquid. A composition of
the first liquid is set such that a resin serving as solute assumes 40 to
80 percent content and that a solvent assumes 60 to 20 percent content.
It is preferable to set the resin content so as to fall within a range
from 40 to 50 percents.

[0098] The second liquid is also set such that a resin (identical with the
resin included in the first liquid) serving as solute assumes 0 to 40
percent content and that a solvent assumes 100 to 70 percent content. It
is preferable to set the resin content so as to fall within a range from
10 to 20 percents. A purpose of application of the second liquid is to
spread the second liquid over the rear surface 1b in a wet fashion in
order to assure an appropriate spread of the high viscosity resin that is
the first liquid to be applied later. Therefore, the second liquid does
not always need to include a resin as solute. As indicated by the
composition mentioned above, the first liquid may also be formed from 0
percent solute content and 100 percent solvent content.

[0099] When the second liquid includes a resin, the second liquid is a low
concentration, low viscosity resin including a resin content that is
lower than that of the first liquid. When the second liquid does not
include a resin, the second liquid is made of only a solvent. In any
case, the second liquid is lower than the first liquid in terms of
viscosity. The second liquid exhibits superior wettability required to
assure an appropriate spread of the first liquid to be applied later.

[0100] Specifically, under the resin-adhesive-layer-backed semiconductor
chip manufacturing method described in connection with the embodiment,
two types of liquids are prepared; namely, the first liquid including at
least a solvent and a resin, and the second liquid whose viscosity is
lower than that of the first liquid. Example configurations for making
the viscosity of the second liquid lower than the viscosity of the first
liquid include the first configuration for making the second liquid from
solely a solvent and the second configuration for making the
concentration of the resin included in the second liquid lower than the
concentration of the resin included in the first liquid. In the first and
second configurations, the second liquid includes the same solvent as
that of the first liquid. In the second configuration, the second liquid
includes the same resin as that of the first liquid, and the
concentration of the resin included in the second liquid is lower than
the concentration of the resin included in the first liquid.

[0101] For convenience's sake, a single type of solvent is used for the
first liquid and the second liquid. However, the solvent of the first
liquid does not always need to be identical with the solvent of the
second liquid. A solvent of another type can also be used for the second
liquid, so long as the solvent has a property of being dissolved in the
first liquid. Likewise, example configurations for making the viscosity
of the second liquid lower than the viscosity of the first liquid include
the third configuration for forming the second liquid from solely a
solvent and the fourth configuration for making the concentration of the
resin included in the second liquid lower than the concentration of the
resin included in the first liquid. In the third and fourth
configurations, the solvent of the second liquid differs in type from the
solvent of the first liquid, and the solvent has a property of being
dissolved in the first liquid. In the fourth configuration, the resin
included in the second liquid is identical with the resin included in the
first liquid. The concentration of the resin included in the second
liquid is lower than the concentration of the resin included in the first
liquid.

[0102] The thus-prepared first and second liquids are supplied, in
sequence of the second liquid and the first liquid, to the semiconductor
wafer 1 on which the lyophobic pattern has been formed. An explanation is
now given to a case where a low viscosity resin including a resin in a
low concentration is used as the second liquid. First, as shown in FIG.
11, the low viscosity resin is applied (ST12). Specifically, as shown in
FIG. 12(b), a low viscosity resin 40a (the second liquid) for the purpose
of mask formation is supplied to the rear surface 1b that is the
processing target surface of the semiconductor wafer 1 on which the
lyophobic pattern is formed from the lyophobic films 3. The high
viscosity resin is now applied (ST13). As shown in FIG. 12(c), in
addition to the low viscosity resin 40a, a high viscosity resin 40b (the
first liquid) including a resin for mask formation in a high
concentration is applied to the rear surface 1b of the semiconductor
wafer 1 over which the low viscosity resin 40a has already been applied.

[0103] Specifically, in the steps (ST12) and (ST13) where the previously
prepared low viscosity resin 40a serving as the first liquid and the high
viscosity resin 40b serving as the second liquid are supplied to the rear
surface 1b, which is the processing target surface of the semiconductor
wafer 1 on which the lyophobic pattern is formed, in sequence of the high
viscosity resin 40b serving as the second liquid and the low viscosity
resin 40a serving as the first liquid. The resin film 40 whose thickness
is larger than the thickness t1 of the lyophobic pattern is thereby
formed in the area R that is surrounded by the lyophobic films 3 and
where the lyophobic pattern is not formed (the resin film formation
step). Details about application of the low viscosity resin 40a and the
high viscosity resin 40b performed in (ST12) and (ST13) are the same as
those described in connection with the low viscosity resin 4a and the
high viscosity resin 4b in the first embodiment by reference to FIG. 8,
and hence their explanations are omitted here for brevity.

[0104] The lyophobic film 3e having the same lyophobic property as that of
the lyophobic films 3 is formed along the contour of the semiconductor
wafer 1 set along the outer edge of the semiconductor wafer 1 to a
predetermined width. Hence, on the occasion of application of the low
viscosity resin 40a and the high viscosity resin 40b, the low viscosity
resin 40a and the high viscosity resin 40b squirted from the respective
dispense nozzles 5A and 5B to the contour of the semiconductor wafer 1
are repelled by the lyophobic film 3e. Consequently, it is possible to
prevent the low viscosity resin 40a and the high viscosity resin 40b from
hanging and falling from the outer edge of the semiconductor wafer 1,
which would otherwise occur when the lyophobic film 3e is not present,
and also prevent staining of the wafer table, which would otherwise be
cause by a drop of the resin.

[0105] In relation to application of the low viscosity resin 40a from the
dispense nozzle 5A and application of the high viscosity resin 40b from
the dispense nozzle 5B, a quantity of resin squirted from the dispense
nozzle 5A and a quantity of resin squirted from the dispense nozzle 5B
may also be controlled according to the area of the square surrounded by
the lyophobic films 3. Specifically, as has been described by reference
to FIG. 5, the quantity of resin squirted from the dispense nozzle 5A and
the quantity of resin squired from the dispense nozzle 5B are controlled
according to application quantity data that specify for each square an
appropriate quantity of resin applied, in association with the area [A]
of the semiconductor chip 1e and the areas [A1] to [A9] of the outer edge
squares 1R(1) to 1R(9). A proportion of the quantity of the low viscosity
resin 40a applied to the quantity of the high viscosity resin 40b applied
is set for each square in such a way that the quantity of the high
viscosity resin 40b applied falls within a range from two to five,
provided that the quantity of the low viscosity resin 40a applied is
taken as one.

[0106]FIG. 14 shows, in an enlarged manner, a state of a contact between
the lyophobic films 3 and the resin film 40 achieved after the resin film
formation step. Although the edges 3a on both widthwise edges of each of
the lyophobic films 3 assume a minute wavelike shape (a saw-toothed
shape), a contour 40c of the resin film 40 (illustrated by broken lines
in FIG. 14) remaining in contact with the edges 3a forms a
substantially-linear, smooth line. The reason for this is that the resin
film 40 exhibits surface tension in a liquid state and also a property of
being impervious to following minute irregularities of the respective
edges 3a because of action of surface tension. The property is very
advantageous in view of formation of a mask having smooth edges. When the
resin film 4 having the smooth contour 40c is treated in the subsequent
baking step, a mask having edges (smooth edges) corresponding to the
contour 40c is formed.

[0107] Subsequently, the thus-applied resin is semi-cured (ST14). The
semiconductor wafer 1 on which the resin film 40 is formed is again sent
to a curing step, where the semiconductor wafer 1 is heated to a
temperature of about 90 degrees centigrade. The resin film 40 is
thus-semi-cured in a state of B stage, whereby a resin adhesive layer 40*
is formed as shown in FIG. 12(d) (a resin adhesive formation step). At
this time, the resin adhesive layer 40* covers an area except for the
area to be removed by means of etching using plasma processing (i.e., the
area of the lyophobic films 3 set along the scribe lines 1c). Therefore,
the resin adhesive layer 40* acts as a mask for etching using plasma
processing. The thickness of the resin adhesive layer 40* is reduced from
the shape of the adhesive layer achieved after application by an amount
equal to the quantity of evaporated solvent.

[0108]FIG. 15 is a cross sectional view of the resin film 40 and the
resin adhesive layer 40*. Since the solvent evaporates from the resin
film 40 in the resin adhesive layer formation step, a thickness t5 of the
resin adhesive layer 40* becomes smaller than a thickness t4 of the resin
film 40. Therefore, adjustment of the thickness t5 of the adhesive resin
layer 40* is adjusted by adjustment of the thickness t4 of the resin film
40; namely, setting the resin content in the low viscosity resin 40a and
the resin content in the high viscosity resin 40b and controlling the
quantity of the low viscosity resin 40a applied and the quantity of the
high viscosity resin 40b applied. The required thickness t5 of the resin
adhesive layer 40* is determined from the thickness of the semiconductor
chip 1e that is an objective of bonding, the thickness of the adhesive
layer achieved after bonding, and the like.

[0109] In the present embodiment, a value of the thickness t5 is
determined from the thickness of an adhesive layer to which the
semiconductor chip 1e is to be die-bonded, and the value of the thickness
t5 preferably ranges from 20 micrometers to 30 micrometers. A
relationship (a contraction factor) between the thickness t4 and the
thickness t5 can be determined by a test, or the like. Accordingly, the
thickness t4 of the resin film 40 required to obtain the required
thickness t5 of the resin adhesive resin layer 40* is determined from the
contraction factor and the thickness t5. When the thickness t4 is
determined, the resin content of the low viscosity resin 4a, the quantity
of low viscosity resin 40a applied, the resin content of the high
viscosity resin 40b, and the quantity of high viscosity resin 40b
applied, all of which are required to achieve the thickness t4, can be
determined by calculation.

[0110] After the resin adhesive layer formation step, the lyophobic
pattern is removed as shown in FIG. 12(e) (ST15). Specifically, there is
performed processing for dissolving the lyophobic pattern formed from the
lyophobic films 3 by means of a solvent, to thus eliminate the lyophobic
pattern from the rear surface 1b (the lyophobic pattern removal step).
Processing is identical with processing pertaining to the lyophobic
pattern removal step described in connection with the first embodiment,
and hence its explanation is omitted here for brevity.

[0111] After the lyophobic pattern removal step, the semiconductor wafer 1
that is a substrate is subjected to plasma etching (ST16). Specifically,
the semiconductor wafer 1 is etched for dicing by means of plasma
processing from the rear surface 1b that is the processing target surface
of the semiconductor wafer 1, until the protective sheet 2 becomes
uncovered (the etching step). The semiconductor wafer 1 is sent to a
plasma processing apparatus, where the rear surface 1b of the
semiconductor wafer 1 is irradiated with a fluorine-based gas plasma P,
such as SF6, (FIG. 12(f)). A portion of the rear surface 1b of the
semiconductor wafer 1, which is not covered with the resin adhesive layer
40* serving as the mask and exposed to the plasma P, is removed by
etching action of the plasma P, whereby the etching trench 1d is formed.
As a result of the etching trench 1d penetrating through an entire
thickness of the semiconductor wafer 1, whereupon the semiconductor wafer
1 is separated into discrete semiconductor chips 1e as shown in FIG.
12(f). After completion of processing pertaining to the etching step, the
semiconductor wafer 1 to which there is affixed the protective sheet 2
for protecting the circuit fabrication surface 1a is separated into a
plurality of semiconductor chips 1f, each of which has the resin adhesive
layer 40* in the state of B stage placed on the rear surface 1b of the
semiconductor chip 1e for use in die-bonding operation.

[0112] During etching using the plasma P, heat of the plasma P exerts on
the resin adhesive layer 40*. As mentioned previously, the resin adhesive
layer 40* is required to hold a semi-cured state of B stage. Hence, in
the course of plasma processing, temperature conditions are required to
be controlled such that a surface temperature of the resin adhesive layer
40* does not exceed a thermosetting temperature (100 degrees centigrade
to 150 degrees centigrade) of a chosen epoxy-based resin. A method used
for controlling the temperature conditions includes appropriately
adjusting plasma processing conditions of a plasma processing apparatus
used; for instance, appropriate adjustment of an output from a high
frequency power unit, or controlling a temperature of the semiconductor
wafer 1 by use of cooling means for circulating a cooling medium through
an interior of electrodes where the semiconductor wafer 1 to be processed
is placed, to thus prevent the temperature of the semiconductor wafer 1
from rising in excess of an appropriate range. A configuration for the
plasma processing apparatus that circulates the cooling medium through
the interior of the electrodes where a processing target is placed in
order to prevent excessive heating of the processing target is a known
technique (see; for instance, JP-A-2004-55703 and JP-A-2007-80912).

[0113] During plasma dicing, the adhesive resin layer 40* (a mask) having
smooth edges is formed. Consequently, a diced edge of each of the
separated discrete semiconductor chips 1e also achieves a smooth,
irregularity-free cut surface. Therefore, it is possible to prevent
occurrence of a defect that would deteriorate reliability of a
semiconductor chip; in other words, a problem that is likely to arise
when a cut surface has a rough shape, or minute cracks attributable to
concentration of stress on minute irregularities.

[0114] Subsequently, the die-bonding sheet 11 is affixed to the resin
adhesive layer 40* (ST17). As shown in FIG. 13(a), the plurality of
semiconductor chips 1f with adhesive resin layers whose circuit
fabrication surfaces 1a are held and affixed to the protective sheet 2
are transferred while the respective resin adhesive layers 40* are
affixed to the die-bonding sheet 11. The die-bonding sheet 11 is
stretched to the annular wafer ring 12a, to thus make up the wafer jig
12.

[0115] The protective sheet 2 is now removed (ST18). Specifically, the
protective sheet 2 is peeled off from the semiconductor chip 1f with a
resin adhesive layer affixed to the die-bonding sheet 11. As shown in
FIG. 13(b), the semiconductor chip aggregate 10 is completed, wherein the
plurality of semiconductor chips 1f with resin adhesive layers, whose
circuit fabrication surfaces 1a are oriented upward and exposed, are held
by the die-bonding sheet 11 from the respective rear surfaces 1b. The
semiconductor chip aggregate 10 is sent in this state to a die bonder. As
shown in FIG. 3(c), the wafer ring 12a is held by the wafer hold
mechanism 13 of the die bonder, whereby the discrete semiconductor chip
1f enters a state in which the discrete semiconductor chip 1 with a resin
adhesive layer can be picked up.

[0116] On the occasion of the picking-up of the semiconductor chip 1f with
the resin adhesive layer, the die-bonding tool 14 and the ejector 15 are
positioned to the semiconductor chip 1f with the resin adhesive layer
that is to be picked up. The ejector pin 16 provided on the ejector 15
pushes the semiconductor chip 1f with the resin adhesive layer to be
taken out from below, and the bonding tool 14 picks up and holds the
semiconductor chip 1f with the resin adhesive layer. The bonding tool 14
has built-in heating means, and the semiconductor chip 1f with the resin
adhesive layer is heated to a predetermined temperature as a result of
being held by the bonding tool 14.

[0117] The bonding tool 14 that holds the thus-picked-up semiconductor
chip 1f with the resin adhesive layer travels to a position above the
heating support 17 that holds the substrate 18 to be bonded. The
substrate 18 is also heated in advance to a predetermined temperature by
a heating mechanism (omitted from the drawings) provided in the heating
support 17. The semiconductor chip 1f with the resin adhesive layer is
aligned to a bonding position, and the bonding tool 14 is lowered,
thereby placing the semiconductor chip 1e on the upper surface of the
substrate 18 by way of the resin adhesive layer 40*. Next, the bonding
tool 14 presses the semiconductor chip 1e against the substrate 18 under
predetermined applied pressure. Thermosetting reaction of the resin
adhesive layer 40* proceeds as a result of the substrate being held in
this state for a predetermined period of time. The semiconductor chip 1e
is bonded to the substrate 18 by means of the resin adhesive layer 40*.

[0118] As mentioned above, in the second embodiment, during manufacture of
semiconductor chips for separating the semiconductor wafer 1 into the
semiconductor chips 1f with adhesive resin layers, which each are formed
from semiconductor devices, by means of etching using plasma processing,
there is employed a method including printing a lyophobic liquid on the
rear surface 1b of the semiconductor wafer 1 that is the other side of
the circuit fabrication surface 1a, along the scribe lines 1c that are
borders between the semiconductor chips 1e, thereby forming a lyophobic
pattern; preparing two types of liquids; namely, the first liquid
including at least a solvent and a resin, and the second liquid whose
viscosity is lower than that of the first liquid; supplying the liquids
over the processing target surface of the semiconductor wafer 1 where the
lyophobic pattern is formed, in descending sequence of the second liquid
and the first liquid, thereby forming the resin film 40 that is thicker
than the lyophobic pattern is formed on the area where the lyophobic
pattern is not formed; semi-curing the resin film 40, to thus form the
resin adhesive layer 40*; and etching, after removal of the lyophobic
pattern from the rear surface of the semiconductor wafer, the rear
surface 1b of the semiconductor wafer 1 while the resin adhesive layer
40* is taken as a mask. As a result, a mask for etching using plasma
processing is formed at low cost, and the mask can also be used as the
resin adhesive layer 40* for die-bonding. Further, the advantage yielded
when the two types of liquids are prepared and applied in two steps as
mentioned in connection with the resin film formation step is also the
same as that yielded in the first embodiment.

[0119] In the first and second embodiments, processing for separating the
semiconductor wafer serving as the substrate into discrete semiconductor
chips by means of plasma dicing has been described as an example
objective of the invention. However, the present invention is not limited
to the processing. The present invention can be applied to processing of
any form, so long as processing is intended for a substrate and requires
formation of a mask in association with etching using plasma processing.
For instance, the present invention can be applied to various types of
processing intended for a substrate; for instance, an example application
for boring via holes in a semiconductor substrate by means of etching
using a plasma, an example application for forming a minute mechanical
device by application of a semiconductor processing technique and through
use of etching using a plasma in a course of manufacture of an MEMS
(Microelectromechanical System); an example application for forming a
circuit pattern on a transparent display panel; and the like.

[0120] The present patent application is based on Japanese Patent
Application (JP-2009-095801) filed on Apr. 10, 2009, the entire subject
matter of which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

[0121] The substrate processing method and the semiconductor chip
manufacturing method of the present invention are characterized in that a
mask for use in etching using a plasma can be formed at low cost. The
methods are useful for processing various substrates, such as processing
for separating a semiconductor wafer serving as a substrate into discrete
semiconductor chips, by means of plasma dicing.